For X-ray imaging, the X-ray source and the X-ray detector have to be positioned in relation to the patient. For example, for moveable X-ray systems, positioning is an important issue in terms of image quality and handling. For positioning, also possible collisions with other equipment or the patient must be avoided. For example, U.S. Pat. No. 4,578,757 describes a device for prevention of collision between a patient table and an X-ray imaging system in form of a movable C-arm. However, estimating and assessing an optimal view is time and X-ray dose consuming. It has been shown further that avoiding collisions is an important process, but requires time and often leads to a change of projection.